请你对以下案例进行分析。 在学习“Although...”这一语言点的时候，有学生出现了这样的句子：“Although I’m not very clever, but I still work hard every day.”老师对他说：“I think you are very clever, because you can say such a great sentence.”之后，又问全班同学：“Don’t you think he is a clever boy”全班同学齐声答道：“Yes!” 接着，又问：“But can you find the difference between his sentence and the 0ne on the blackboard”几秒钟的思考之后，许多同学发现了错误，回答道“There should be no ’but’ in the sentence.”